Wind turbine blades of fibre-reinforced polymer are usually manufactured in moulds, where the top side and the bottom side of the blade profile are manufactured separately by arranging glass fibre mats in each of the two mould parts. Then, the two halves are glued together, often by means of internal flange parts. Glue is applied to the inner face of the lower blade half before the upper blade half is lowered thereon. Additionally, one or two reinforcing profiles (beams) are often attached to the inside of the lower blade half prior to gluing to the upper blade half.
It is commonly known that moulds for making large articles such as wind turbine blades and consisting of two mould parts are closed about a longitudinal hinge line, where the hinges are passive, i.e. a crane is used to lift one of the mould parts about the hinge line for closure and opening of the mould. When making wind turbine blades, the mould is closed so as to glue two blade shell halves together, said shell halves being produced in separate mould parts.
DK 171.948B discloses a method for manufacturing turbine blades, where the two mould parts are hinged together along a hinge line coinciding with the finished leading edge of the blade. One disadvantage of said method and shape is that it is only suitable for manufacturing profiled members with a rectilinear edge coinciding with the hinge line of the mould. The closing procedure is not mentioned at all in this reference.
The Danish Utility Model BR 2004 00032 discloses an assembly, where a drive unit is built into the hinge structure lifting and turning one of the mould parts from a position, in which its opening faces upwards, to a position above the other mould part, in which the openings of the two mould parts face each other. The closure mechanism includes an additional assembly bringing the two mould parts together in a rectilinear movement by means of a parallel linkage mechanism. This curve linear or almost rectilinear closing movement is necessary when manufacturing wind turbine blades, since a complete closure by rotation is geometrically impossible unless the hinge axis is arranged at a disadvantageously large distance from the mould cavity.
WO 04/43679 discloses a mould assembly, where the above-mention rectilinear closing movement is accomplished by means of protractile guide rods mounted on one of the two mould parts along the two longitudinal sides extending parallel to the hinge lines, and associated bearing means along the longitudinal sides of the second of the two mould parts. This assembly allows for an assembly of the two mould parts with very high accuracy.
Wind turbine blades have become increasingly longer of the years and may reach up to 60 meters or even more today, which means that mould assemblies for moulding said blades have also become increasingly larger. This results in problems for prior art mould assemblies, since the mould part rotating with respect to the other one during closure of the mould assembly reaches a very great height during the rotary motion, which may mean that the height of the ceiling in the halls where the blades are manufactured must be very great. This means that the halls become more expensive to build, or that the ceilings in existing halls have to be raised, which of course also results in higher financial costs.